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S E Douglas

Publications and source records attributed to S E Douglas.

At least 19 recordsLinked to original sources
PubMed2006

Characterization of a partial alpha-amylase clone from red porgy (Pagrus pagrus): expression during larval development.

A partial alpha-amylase cDNA was isolated from red porgy (Pagrus pagrus, Teleostei: Sparidae) and its tissue specific expression during larval development was examined. The cDNA was 949 bp long and showed 90% identity with other fish amylases. A 545 bp fragment was used to study amylase expression using in situ hybridization and RT-PCR techniques. Both methods showed a similar pattern: high and relatively constant expression for the first 30 days after hatching (dah), subsequently decreasing until the end of the experiment at 60 dah. The goal of this work was to extend the existing knowledge of the functionality of larval fish digestive systems and to provide new information about alpha-amylase gene expression.

Age Factors↗
PubMed2004

Identification of immune-relevant genes from atlantic salmon using suppression subtractive hybridization.

In order to probe the interaction between an invading microorganism and its host, we have investigated differential gene expression in Atlantic salmon (Salmo salar) experimentally infected with the pathogen Aeromonas salmonicida, the causative agent of furunculosis. Subtractive cDNA libraries were constructed by suppression subtractive hybridization (SSH) from 3 immune-relevant tissues at 2 time points during the infection process. Both forward- and reverse-subtracted libraries were generated, and approximately 200 clones were sequenced from each library, giving a total of 1778 expressed sequence tags (ESTs), which were annotated according to functional categories and deposited in GenBank (BQ035314-BQ037059). Numerous genes involved in signal transduction, innate immunity, and other processes have been uncovered in the subtractive libraries. These include known acute-phase reactants, along with more novel genes encoding proteins such as tachylectin, hepcidin, precerebellin-like protein, O-methyltransferase, a putative saxitoxin-binding protein, and others. A subset of genes that were represented in the subtracted libraries was further analyzed by virtual Northern, or reverse transcription-polymerase chain reaction (RT-PCR) assays to verify their differential expression as a result of infection.

Aeromonas salmonicida↗
PubMed2004

Trypsinogen expression during the development of the exocrine pancreas in winter flounder (Pleuronectes americanus).

Histological, biochemical and molecular techniques were used to describe the functional development of the pancreas in winter flounder (Pleuronectes americanus) with specific reference to the expression of three trypsinogen genes. The pancreas was identified shortly following hatch, appearing as a compact structure situated dorsal and slightly posterior to the liver. As the larval fish approached metamorphosis, the pancreas became diffuse, spreading throughout the mesentery surrounding the stomach, the upper intestine and the pyloric caecae. Trypsin 2 expression was detected from 5 days post-hatch (dph). Two other related trypsinogen genes isolated from the pyloric caecae (Trypsin 1) and the intestine (Trypsin 3) showed contrasting results. Trypsin 1 showed very low levels of expression and only in late larval stages and metamorphosis. Trypsin 3 showed expression only after 20 dph. In order to determine tissue-specific expression of the three trypsinogen genes, the RNA from seven gastrointestinal-associated tissues was examined. Trypsin 1 and Trypsin 2 expression was most notably associated with the pyloric caecae, cardiac stomach, pyloric stomach and the rectum, although some variation in expression level between tissues was observed. Trypsin 3 expression had a narrower tissue distribution and was only associated with the pyloric caecae and the rectum. The tissue expression patterns observed here are likely due in part to the diffuse nature of the pancreas. Trypsin-like activity was evident from hatch and continued at significant levels through to at least 25 dph.

Animals↗
PubMed2001

Cloning and developmental expression of a family of pleurocidin-like antimicrobial peptides from winter flounder, Pleuronectes americanus (Walbaum).

Low molecular weight antimicrobial peptides are an important component of the innate immune system in animals, yet they have not been examined widely in fish. Of particular interest is their expression during development and in response to environmental conditions and disease. Here, we report the isolation of four genomic sequences encoding putative antimicrobial peptides from the winter flounder, Pleuronectes americanus (Walbaum), as well as reverse transcription-PCR products from two tissues that form the first defensive barrier to microbes - skin and intestine. Alignment of the predicted polypeptide sequences shows a conserved hydrophobic signal peptide of 22 amino acids followed by 25 amino acids that are identical (WF2) or homologous to the amino acid sequence of pleurocidin, followed by a conserved acidic portion. Southern hybridisation analysis indicates that related peptides are encoded in the genomes of other flatfish species. Northern and RT-PCR analyses of RNA from multiple tissues show that two of the pleurocidin genes are expressed predominantly in the skin whereas two other genes are expressed mainly in the intestine. RT-PCR assays of total RNA from larvae of different ages provide the first evidence of developmental expression of antimicrobial peptides in fish and indicate that the pleurocidin gene is first expressed at 13 days post-hatch in winter flounder.

Amino Acid Sequence↗
PubMed1999

The plastid genome of the cryptophyte alga, Guillardia theta: complete sequence and conserved synteny groups confirm its common ancestry with red algae.

The plastid genome of the cryptophyte alga Guillardia theta (121,524 bp) has been completely sequenced. The genome is 33% G+C and contains a short, nonidentical inverted repeat (4.9 kb) encoding the two rRNA cistrons. The large and small single-copy regions are 96.3 and 15.4 kb, respectively. Forty-six genes encoding proteins for photosynthesis, 5 genes for biosynthetic function, 5 genes involved in replication and division, 30 tRNA genes, 44 ribosomal protein genes (26 large subunit and 18 small subunit), 3 translation factors, 8 genes encoding components of the transcriptional machinery including 3 ycfs (hypothetical chloroplast frames), and 26 additional ycfs have been identified. There are eight ORFs larger than 50 amino acids, 3 of which have homologues on the plastid genome of the rhodophyte, Porphyra purpurea (Reith and Munholland 1995) and/or the Synechocystis genome (Kaneko et al. 1996) and can be designated new ycfs. Intergenic spacers are very short, no introns have been detected, and several genes overlap, all resulting in a very compact genome. In addition, large clusters of genes (such as those for the ribosomal proteins) are organized into single transcriptional units (Wang et al. 1997), again resulting in an economically organized genome. The cryptophyte plastid genome is almost completely comprised of clusters of genes that are found on the rhodophyte Porphyra purpurea, confirming its common ancestry with red algae. Furthermore, recombination events involving both tRNA genes and the rRNA cistrons appear to have been responsible for the structure of the cryptophyte plastid genome, including the formation of the inverted repeat.

Cell Division↗
PubMed1999

The secondary endosymbiont of the cryptomonad Guillardia theta contains alpha-, beta-, and gamma-tubulin genes.

Cryptomonads have acquired photosynthesis through secondary endosymbiosis: they have engulfed and retained a photosynthetic eukaryote. The remnants of this autotrophic symbiont are severely reduced, but a small volume of cytoplasm surrounding the plastid persists, along with a residual nucleus (the nucleomorph) that encodes only a few hundred genes. We characterized tubulin genes from the cryptomonad Guillardia theta. Despite the apparent absence of microtubules in the endosymbiont, we recovered genes encoding alpha-, beta-, and gamma-tubulins from the nucleomorph genome of G. theta. The presence of tubulin genes in the nucleomorph indicates that some component of the cytoskeleton is still present in the cryptomonad symbiont despite the fact that very little cytoplasm remains, no mitosis is known in the nucleomorph, and microtubules have never been observed anywhere in the symbiont. Phylogenetic analyses with nucleomorph alpha- and beta-tubulins support the origin of the cryptomonad nucleomorph from a red alga. We also characterized alpha and beta-tubulins from the host nucleus of G. theta and compared these with tubulins we isolated from two flagellates, Goniomonas truncata and Cyanophora paradoxa, previously proposed to be related to the cryptomonad host. Phylogenetic analyses support a relationship between the cryptomonad host and Goniomonas but do not support any relationship between cryptomonads and Cyanophora.

Base Sequence↗
PubMed1998

Plastid evolution: origins, diversity, trends.

The amazing diversity of extant photosynthetic eukaryotes is largely a result of the presence of formerly free-living photosynthesizing organisms that have been sequestered by eukaryotic hosts and established as plastids in a process known as endosymbiosis. The evolutionary history of these endosymbiotic events was traditionally investigated by studying ultrastructural features and pigment characteristics but in recent years has been approached using molecular sequence data and gene trees. Two important developments, more detailed studies of members of the Cyanobacteria (from which plastids ultimately derive) and the availability of complete plastid genome sequences from a wide variety of plant and algal lineages, have allowed a more accurate reconstruction of plastid evolution.

Biological Evolution↗
PubMed1997

The large ribosomal protein gene cluster of a cryptomonad plastid: gene organization, sequence and evolutionary implications.

The complete sequence of the major ribosomal protein gene cluster of the plastid genome of the cryptomonad alga Guillardia theta (formerly Cryptomonas phi) is presented. The ribosomal protein genes (corresponding to the S10, spc, alpha and L13/S9 operons of E. coli) are found upstream of the previously reported plastid str operon, and transcribed in the same orientation. The genes are very tightly packed with as little as two nucleotides between the rpl14 and rpl24 genes. The gene arrangement is very similar to that reported for the rhodophyte alga, Porphyra purpurea, and the chromophyte diatom, Odontella sinensis, indicating a close evolutionary relationship between these groups of algae. Northern analysis indicates that the 29 genes are arranged as one operon and are transcribed as a single mRNA that is subsequently processed into smaller transcripts.

Amino Acid Sequence↗
PubMed1995

DNA Strider. An inexpensive sequence analysis package for the Macintosh.

DNA Strider is a user-friendly Macintosh program designed for analysis of molecular sequence data. The program shows great versatility in choice of genetic codes, restriction enzymes, algorithms for hydropathy plots, and interconversions between types of sequence data. It is very straightforward and interacts well with other sequence and phylogenetic analysis packages, importing and exporting data easily. The graphic outputs can be used directly for manuscript-quality figures, or exported to more sophisticated text or graphic programs.

Amino Acid Sequence↗
PubMed1994

Genetic relatedness of toxic and nontoxic isolates of the marine pennate diatom Pseudonitzschia (Bacillariophyceae): phylogenetic analysis of 18S rRNA sequences.

The nuclear small subunit (SSU) rRNA genes from several marine diatoms, including 2 species that have been responsible for toxic blooms, were amplified from total DNA by the polymerase chain reaction (PCR), and the sequences analysed to determine their genetic relatedness. The isolates investigated include 2 morphologically similar forms of the pennate diatom Pseudonitzschia pungens: (1) P. pungens f. multiseries, a known producer of the toxin domoic acid, and (2) P. pungens f. pungens, which is not toxic. Strains of a second toxin-producing species, P. australis, and a nontoxic Thalassiosira species were also included in this study. Phylogenetic analyses of sequences by both distance and parsimony methods clearly distinguished the 2 forms of P. pungens and the 2 Pseudonitzschia species from other diatoms for which sequence data are available. Differences in the nucleotide sequences of the 2 forms of P. pungens permitted the design of PCR primers that allowed discrimination between them. This may prove a valuable tool in identifying toxic and nontoxic forms of closely related and morphologically similar diatom species.

Base Sequence↗
PubMed1994

The photosynthetic endosymbiont in cryptomonad cells produces both chloroplast and cytoplasmic-type ribosomes.

Cryptomonad algae contain a photosynthetic, eukaryotic endosymbiont. The endosymbiont is much reduced but retains a small nucleus. DNA from this endosymbiont nucleus encodes rRNAs, and it is presumed that these rRNAs are incorporated into ribosomes. Surrounding the endosymbiont nucleus is a small volume of cytoplasm proposed to be the vestigial cytoplasm of the endosymbiont. If this compartment is indeed the endosymbiont's cytoplasm, it would be expected to contain ribosomes with components encoded by the endosymbiont nucleus. In this paper, we used in situ hybridization to localize rRNAs encoded by the endosymbiont nucleus of the cryptomonad alga, Cryptomonas phi. Transcripts of the endosymbiont rRNA gene were observed within the endosymbiont nucleus, and in the compartment thought to represent the endosymbiont's cytoplasm. These results indicate that the endosymbiont produces its own set of cytoplasmic translation machinery. We also localized transcripts of the host nucleus rRNA gene. These transcripts were found in the nucleolus of the host nucleus, and throughout the host cytoplasm, but never in the endosymbiont compartment. Our rRNA localizations indicate that the cryptomonad cell produces two different of sets of cytoplasmic-type ribosomes in two separate subcellular compartments. The results suggest that there is no exchange of rRNAs between these compartments. We also used the probe specific for the endosymbiont rRNA gene to identify chromosomes from the endosymbiont nucleus in pulsed field gel electrophoresis. Like other cryptomonads, the endosymbiont nucleus of Cryptomonas phi contains three small chromosomes.

Base Sequence↗
PubMed1992

A secY homologue is found in the plastid genome of Cryptomonas phi.

An open reading frame with significant similarity to the secY gene of Escherichia coli has been found within a ribosomal protein operon on the plastid genome of the chlorophyll c-containing alga Cryptomonas phi. The gene encodes a protein of 420 amino acids (molecular weight 46,906 daltons) and contains ten potential membrane-spanning domains, as in the E. coli homologue. This report of a secY homologue in a plastid genome provides preliminary evidence that a prokaryotic-like protein export system may be operating in plastids.

Amino Acid Sequence↗
PubMed1992

Eukaryote-eukaryote endosymbioses: insights from studies of a cryptomonad alga.

It has been proposed that those plants which contain photosynthetic plastids surrounded by more than two membranes have arisen through secondary endosymbiotic events. Molecular evidence confirms this proposal, but the nature of the endosymbiont(s) and the number of endosymbioses remain unresolved. Whether plastids arose from one type of prokaryotic ancestor or multiple types is the subject of some controversy. In order to try to resolve this question, the plastid gene content and arrangement has been studied from a cryptomonad alga. Most of the gene clusters common to photosynthetic prokaryotes and plastids are preserved and seventeen genes which are not found on the plastid genomes of land plants have been found. Together with previously published phylogenetic analyses of plastid genes, the present data support the notion that the type of prokaryote involved in the initial endosymbiosis was from within the cyanobacterial assemblage and that an early divergence giving rise to the green plant lineage and the rhodophyte lineage resulted in the differences in plastid gene content and sequence between these two groups. Multiple secondary endosymbiotic events involving a eukaryotic (probably rhodophytic alga) and different hosts are hypothesized to have occurred subsequently, giving rise to the chromophyte, cryptophyte and euglenophyte lineages.

Amino Acid Sequence↗